This invention relates generally to flooring tools, and in particular to motorized floor stripper machines.
Floor stripper machines are used to strip flooring materials that are glued down to concrete or wood subfloors. FIG. 1 shows a prior art stripper machine 10 that is made with a frame 12, a blade carrier 14, a blade 16, and an electric motor 18. FIG. 2 is a partial bottom view of stripper machine 10, showing how rotational energy generated by the motor spindle 19 is translated into an orbital motion by attaching a cam 20 (eccentric) to the spindle 19. Cam 20 is inserted into a plate 22 that forms a linkage between the cam 20 and a blade carrier 14. Thus the orbital motion of the cam 20 is transferred by the plate 22 to a blade carrier 14, which moves the blade 16 in an orbital motion which is useful for stripping the flooring from the subfloor. As shown in FIG. 1, blade 16 is clamped down on to the blade carrier 14 (at bottom) by blade clamp 26 (on top) by fasteners 28. The prior art blade carrier and blade clamp are both rectangular in shape and about as wide as a prior art blade. In operation, the user pushes the machine at the handles 24, and the orbital motion of the blade 16 assists in stripping the flooring off the subfloor.
Different forms of linkage between the cam and the blade carrier can be used to produce different forms of motion in the blade. In some early stripper machines, the linkage is formed by the cam element simply contacting the blade carrier from behind and pushing the blade carrier in a forward direction. In later machines, the cam is inserted in a plate to form a linkage, and the plate is connected to the blade carrier by way of fasteners. When only a single plate is used to form the linkage to the blade carrier, the orbital motion of the cam is transferred directly to the blade carrier. As a result, the blade carrier and blade move in an orbital motion with both left-to-right and forward and backward components. However, it is mainly the forward component that is useful in stripping the flooring. The left to right motion causes extra vibration, and can combine with the centrifugal force of the motor itself to cause the machine to turn towards the user's right. In such case, the user has to counteract the turning by steering the machine against it, which requires extra effort. For this reason, alternative forms of linkage have been developed to minimize the undesirable left to right motion, and others have been developed to produce only forward and backward motion in the blade carrier.
In many of the existing motorized floor stripper machines, the linkages between the cam element and the blade carrier element have durability problems, while others produce undesirable left to right motion in the blade carrier which must be controlled. For example, pushing linkages present durability problems. The constant rubbing of the cam against a back side surface of a blade carrier wears out these parts, and the springs necessary to hold the blade carrier in contact with the cam also wear out quickly. It may be preferable to insert the cam within a plate to form the linkage, and then use the plate to impart the motion of the blade carrier. However, inserting the cam into such a plate produces the undesirable left to right motion when the plate is connected to the blade carrier. Some prior art motorized floor stripper machines use a linkage in which the cam is connected to a first drive plate, and the first drive plate is connected to a second drive plate fixedly connected to the blade carrier by way of an additional pivot. In conjunction with the additional pivot, these machines include costly slide bearings to eliminate any undesirable left to right motion in the blade carrier.
To limit the left to right portion of the motion produced by the cam, as just mentioned, some prior art motorized floor stripper machines have included slide bearings with a long arm or rod that moves forward and backward within a sleeve. Other prior art motorized floor stripper machines reciprocate an arm portion of their blade carrier element within a channel of a housing. Still others use a control arm connected to one side of the frame that forms a forward pivot to limit the left to right motion. However, devices employing slide bearings, reciprocating arms, or a control arm are easily damaged if the machine is dropped on its blade carrier element. The problem of dropping of the machine on its blade carrier can often occur on a jobsite. The machines are normally transported around a job by rocking them back on their rear wheels and pushing them. If the user is not careful to lower the machine gently back down onto the blade carrier, then bending of slide bearings, blade carrier arms, or control arms can result. If these elements become bent, they will no longer function properly and can be very expensive to repair.
To prevent the blade carrier or connected components from being damaged if the front of the stripper machine is dropped, it would be desirable to have some sort of shock absorber between the frame of the machine and the blade carrier that could absorb some of the impact. Some existing motorized floor stripper machines use elastomeric shock absorbers, but a problem with these shock absorbers is that they sometimes do not provide sufficient resistance for efficient stripping of tough or hard materials. For example, in the stripping of hardwood or ceramic tile floors, the resistance encountered by the blade and transferred back to the shock absorbers by the blade carrier may be greater than the shock absorbers can counteract. As a result, despite the continuing motion of the cam, the blade carrier recoils against the shock absorbers, which give and allow the blade carrier to move backwards. In this situation, the forward motion of the blade is effectively stopped. Therefore, if the machine is to employ shock absorbers between the frame and the blade carrier, it would be desirable to additionally provide a means to guide the motion of the blade carrier so that it can move only with the motion of the cam. This would improve the effectiveness of the stripping motion of the machine.
The blade carrier of prior art stripper machines have typically been made in two parts: a bottom blade carrier and a top blade clamp. The top blade clamp is fastened down on top of the blade using screws that thread into the bottom blade carrier. A problem with many of these devices is that they use a blade carrier that has a rectangular shape and is quite wide, about as wide as the blade itself. However, if a substantially narrower blade is installed on such a wide blade carrier, the blade carrier itself may contact areas of the floor that have not yet been stripped by the narrower blade. This can create significant unnecessary resistance.
As an example, as shown in FIG. 1, it would be desirable to mount narrower blades onto blade carrier 14 for removal of tougher or harder materials, such as wood or ceramic tile. This is because the machine is only powerful enough to strip up only a narrow row of the material. However, when only a narrow row is stripped, a rectangular blade carrier that is wider than the blade can impact the unstripped material on either side of the row, creating unnecessary resistance. Moreover, the blade carrier can be held up at an elevation as it contacts the top surface of unstripped material on either side of the row, which can prevent the blade from getting beneath the material being stripped.
An additional problem with existing blade carriers that have only two wide set blade clamp holes for clamping a single type of wide blade is that they do not function well with narrower blades. If the blade clamp fasteners are not positioned at least close in proximity to the width of the blade (more ideally through holes or slots provided in the actual blade), the blade can slip backward when it contacts tough or hard materials. Furthermore, if the upper blade clamp is not clamped down very tightly at least in the area of the blade, the upper blade clamp can get debris built-up beneath it that can form a wedge and cause damage.
For these reasons, it would be desirable for the blade carrier and blade clamp to include a number of mounting positions for a number of blades of various widths, particularly blades having substantially narrower widths than prior art blades. Furthermore, it would be desirable for the outer edge of the blade clamp and blade carrier to include a shape that would allow the blade carrier and blade clamp to follow behind a substantially narrower blade without contacting areas of the floor which are not yet stripped, such as either side of a previously stripped row of hardwood or ceramic tile flooring.
The figures depict various embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.